New analysis shows that the Chandler Wobble in Earths axis changed phase by 180 degrees in 2005. The question is why.

If you travel to the Arctic and attempt to find the axis of Earths rotation, youll notice something odd. The position of this axis on Earths surface moves with a period of about seven years. This is the combined result of two effects. The one were interested today is called the Chandler Wobble, which has a period of 433 days and was discovered by American astronomer Seth Carlo Chandler in 1891.

The Chandler Wobble is reasonably well understood. Any spinning sphere that it is not entirely spherical should wobble in this way. However, on Earth, the wobble varies in amplitude from decade to decade, a motion that is thought to be the result of the changes in pressure at the bottom of the oceans caused by fluctuations in salinity, temperature, and ocean circulation.

But there is also something mysterious about the Chandler Wobble. In 1920, it underwent a sudden phase change of 180 degrees. Nobody knows why.

Now a new analysis of data on Earths rotation going back 160 years indicates that this event was not unique. Zinovy Malkin and Natalia Miller at the Russian Academy of Sciences Central Astronomical Observatory in Pulkovo say the phase has changed by small amounts on many occasions during this time. But the big news is that the wobble underwent 180-degree changes in phase on two other occasions: once in 1850 and the other in 2005.

So why should the Chandler Wobble undergo these changes in phase? An interesting puzzle for anybody with a few brain cycles to spare.

Investigations of the anomalies in the Earth rotation, in particular, the polar motion components, play an important role in our understanding of the processes that drive changes in the Earth’s surface, interior, atmosphere, and ocean. This paper is primarily aimed at investigation of the Chandler wobble (CW) at the whole available 163-year interval to search for the major CW amplitude and phase variations. First, the CW signal was extracted from the IERS (International Earth Rotation and Reference Systems Service) Pole coordinates time series using two digital filters: the singular spectrum analysis and Fourier transform. The CW amplitude and phase variations were examined by means of the wavelet transform and Hilbert transform. Results of our analysis have shown that, besides the well-known CW phase jump in the 1920s, two other large phase jumps have been found in the 1850s and 2000s. As in the 1920s, these phase jumps occurred contemporarily with a sharp decrease in the CW amplitude.

Journal reference: Earth Planets Space, 2010, v. 62, No. 12, 943-947

2
posted on 02/23/2013 1:33:22 PM PST
by SunkenCiv
(Romney would have been worse, if you're a dumb ass.)

This is the name given to the movement of the earth’s pole by 0.7 arcseconds over a period of about 14 months. For more information, visit a site over at the National Radio Astronomy Obserrvatory and check out the IEPS Bulletin at the U.S. Naval Observatory which predicts the earth polar wander based on a mathematical model. Chandler Wobble is a periodic phenomenon which means that it can be modeled by ‘simply’ fitting a harmonic series of sines or cosines to the past record of deflections, and then using this empirical model to make limited forecasts into the future. From what I understand of the technical literature, the cause of this wobble is believed to reside in the natural resonances in the body of the spinning earth due to the detailed distribution of mass in its surface, interior, oceans and atmosphere. This system has a ‘14-month’ harmonic which can be excited through a complex pattern of forcings by the moon, sun and sudden crustal rearrangements (earthquakes). There are many distinct periodic excitations by the sun and moon and their changing distances and tidal forcings, and these result in distinct monthly, yearly and multi-year periodicities in the polar wander. The Chandler Wobble may be a natural harmonic resonance that is also stimulated by these other constant lunar-solar forcings at the natural resonance frequency of the solid earth.

5
posted on 02/23/2013 1:35:48 PM PST
by SunkenCiv
(Romney would have been worse, if you're a dumb ass.)

Jake: No, I didn’t. Honest... I ran out of gas. I... I had a flat tire. I didn’t have enough money for cab fare. My tux didn’t come back from the cleaners. An old friend came in from out of town. Someone stole my car. There was an earthquake. A terrible flood. Locusts! IT WASN’T MY FAULT, I SWEAR TO GOD!

it's constantly raining at the equator, somewhere, every day ~ there's an enormous belt of storms there. As mountains and other land masses rise the rain comes down and dissolves a little bit ~ the water eventually flows into the world ocean a tad heavier than when it fell due to its salt content.

That could easily account for the creation of the pressure on the ocean bottom that drives the wobble.

With only a couple of major data points we don't know if this is related to anything in particular ~ I do believe this measurement is near the limits of quantum noise.

It spins left for me unless I change it. I am left handed. which means I am (for the moment) in my right mind. Lefties of the world UNITE! Left is right!

And did you know? Everyone is born right-handed.

Only the greatest can overcome it.

Interestingly, if I do something like typing, and “think” about what I am typing, while sorta half looking at the girl she swings her leg back and forth. So now I’m a wondering if I can get her to STOP.

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